CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of, and priority to,
U.S. Provisional Patent Application Serial No. 62/332,287, filed May 5, 2016,
U.S. Provisional Patent Application Serial No. 62/381,952, filed August 31, 2016,
U.S. Provisional Patent Application Serial No. 62/438,212, filed December 22, 2016, and
U.S. Provisional Patent Application Serial No. 62/449,114, filed January 23, 2017, the contents of these applications being incorporated entirely herein by reference.
FIELD OF THE INVENTION
[0002] The present disclosure relates generally to systems and methods for correcting vision,
and more particularly, to systems and methods that employ implants to reshape the
cornea in order to correct vision.
BACKGROUND
[0003] A variety of eye disorders, such as myopia, hyperopia, astigmatism, and presbyopia,
involve abnormal shaping of the cornea. This abnormal shaping prevents the cornea
from properly focusing light onto the retina in the back of the eye (i.e., refractive
error). A number of treatments attempt to reshape the cornea so that the light is
properly focused. For instance, a common type of corrective treatment is LASIK (laser-assisted
in situ keratomileusis), which employs a laser to reshape the cornea surgically.
SUMMARY
[0004] According to aspects of the present disclosure, embodiments employ implants to reshape
the cornea in order to correct vision. For instance, such embodiments may address
the refractive errors associated with eye disorders such as myopia, hyperopia, astigmatism,
and presbyopia. The implants may be formed from natural tissue, such as donor corneal
tissue.
[0005] According to an example embodiment, a system for forming corneal implants includes
a first cutting apparatus configured to cut a donor cornea and form a portion of corneal
tissue. The donor cornea includes an anterior surface and a posterior surface. The
first cutting apparatus is configured to cut the donor cornea along an axis extending
between the anterior surface and the posterior surface. The system also includes a
second cutting apparatus configured to form a plurality of lenticules from the portion
of corneal tissue by making, to the portion of corneal tissue, a series of cuts transverse
to the axis. Corneal tissue between consecutive cuts by the second cutting apparatus
provides a corresponding lenticule to be shaped for a corneal implant. A distance
between the consecutive cuts defines a thickness for the corresponding lenticule.
[0006] According to another example embodiment, a method for forming corneal implants includes
providing a donor cornea including an anterior surface and a posterior surface. The
method includes forming, with a first cutting apparatus, a portion of corneal tissue
by cutting the donor cornea along an axis extending between the anterior surface and
the posterior surface, the method includes forming, with a second cutting apparatus,
a plurality of lenticules from the portion of corneal tissue by making, to the portion
of corneal tissue, a series of cuts transverse to the axis. Corneal tissue between
consecutive cuts by the second cutting apparatus provides a corresponding lenticule
to be shaped for a corneal implant. A distance between the consecutive cuts defines
a thickness for the corresponding lenticule. The method may further include freezing
the portion of corneal tissue, wherein the second cutting apparatus includes a cryo-microtome
configured to cut the frozen portion of corneal tissue.
[0007] In the example embodiments, the consecutive cuts made by the second cutting apparatus
include a first cut made closest to the anterior surface of the donor cornea and a
second cut made closest to the posterior surface of the donor cornea. The corresponding
lenticule includes a first surface formed by the first cut and a second surface formed
by the second cut. The second cutting apparatus may be further employed to shape at
least one of the first surface or the second surface of the corresponding lenticule
to form the corneal implant with a desired refractive profile.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
FIG. 1A illustrates a view of an example implant formed from natural tissue according
to aspects of the present disclosure.
FIG. 1B illustrates another view of the example implant of FIG. 1A.
FIG. 2 illustrates an example procedure employing an inlay implant formed from natural
tissue, according to aspects of the present disclosure.
FIG. 3 illustrates an inlay implanted within corneal tissue, according to aspects
of the present disclosure.
FIG. 4A illustrates an example procedure employing an onlay implant formed from natural
tissue, according to aspects of the present disclosure.
FIG. 4B illustrates another example procedure employing an onlay implant formed from
natural tissue, according to aspects of the present disclosure.
FIG. 4C illustrates yet another example procedure employing an onlay implant formed
from natural tissue where one or more holes are formed in the Bowman's membrane, according
to aspects of the present disclosure.
FIG. 5 illustrates an onlay implanted under a corneal epithelium, according to aspects
of the present disclosure.
FIG. 6 illustrates an example implant for addressing surface irregularities, according
to aspects of the present disclosure.
FIG. 7A illustrates a view of another example implant for addressing surface irregularities,
according to aspects of the present disclosure.
FIG. 7B illustrates another view of the example implant of FIG. 7A.
FIG. 8 illustrates an example system for delaminating a donor cornea, according to
aspects of the present disclosure.
FIG. 9 illustrates an example system for reshaping a lenticule, according to aspects
of the present disclosure.
FIG. 10 illustrates an example approach for reshaping a lenticule, according to aspects
of the present disclosure.
FIGS. 11A-B illustrate an example implantation of an implant employing a flap with
a single attached portion.
FIGS. 12A-B illustrate an example implantation of an implant employing a flap with
a plurality of attached portions arranged symmetrically about the flap, according
to aspects of the present disclosure.
FIG. 13A illustrates another example system for forming a plurality of lenticules
from a cornea, according to aspects of the present disclosure.
FIG. 13B illustrates an embodiment of the example system of FIG. 13A, according to
aspects of the present disclosure.
FIG. 13C illustrates another embodiment of the example system of FIG. 13A, according
to aspects of the present disclosure.
FIG. 14 illustrates an example implant with an edge (e.g., randomly serrated) designed
to minimize glare and halo effect, according to aspects of the present disclosure.
[0009] While the invention is susceptible to various modifications and alternative forms,
a specific embodiment thereof has been shown by way of example in the drawings and
will herein be described in detail. It should be understood, however, that it is not
intended to limit the invention to the particular forms disclosed, but on the contrary,
the intention is to cover all modifications, equivalents, and alternatives falling
within the spirit of the invention.
DESCRIPTION
[0010] Example systems and methods employ implants to reshape the cornea in order to correct
vision. For instance, such embodiments may address the refractive errors associated
with eye disorders such as myopia, hyperopia, astigmatism, and presbyopia.
[0011] Example systems and methods employ implants that are formed from natural tissue.
In particular, the implants may be formed from donor corneal tissue. For instance,
the implants may be formed as allografts, i.e., tissue that is transplanted between
members of the same species. Alternatively, the implants may be formed as xenografts,
i.e., tissue that is transplanted between members of different species.
[0012] The methods and implants of the present disclosure exhibit significant improvements
over prior attempts to correct vision utilizing implants. For example, some prior
attempts to correct vision utilized implants made from synthetic materials; however,
such implants made from synthetic materials did not work well for a variety of reasons
(e.g., the irregularity of the collagen matrix of an eye, differences in the state
of hydration of the synthetic material and the collagen matrix of an eye, lack of
biocompatibility, etc.). The methods and implants of the present disclosure, which
are made from natural tissue, overcome the deficiencies of such prior attempts. In
particular, for example, the methods and implants of the present disclosure, which
are made from natural tissue, exhibit greater biocompatibility with a patient's cornea,
more closely match the index of refraction of the patient's cornea, can be maintained
at a state of hydration that is required for implantation (e.g., a state of hydration
that is similar to that of the implantation site), and ensures that sufficient gas
and nutrients can be exchanged within the patient's cornea. Such advantages have not
been achieved or successfully commercialized, at least in part, due to a lack of suitable
methods and systems for manufacturing implants made from natural tissue.
[0013] FIGS. 1A and 1B illustrate an example implant 10 according to aspects of the present
disclosure. The implant 10 is formed from natural tissue or, more particularly, for
example, a donor cornea. As shown in FIG. 1A, the implant 10 has a front (anterior)
surface 12 corresponding to the anterior of the eye when implanted and a back (posterior)
surface 14 corresponding to the posterior of the eye when implanted. While the example
implant 10 illustrated in FIG. 1 has a front surface 12 and back surface 14 that form
a meniscus shape, the implant 10 may have a plano-convex shape, a plano-concave shape,
a bi-convex shape, or the like. Additionally, the front surface 12 and/or the back
surface 14 may be spherical and/or aspherical.
[0014] To facilitate description of some aspects of the implant 10, FIG. 1B shows a top
plan view of the implant 10 having a central region 34, a mid-peripheral region, 36,
an outer peripheral region 37, and a peripheral edge 32. It should be understood that
such regions 34, 36, 37 are intended as one non-limiting example and the implants
10 may have any number (i.e., one or more) of regions of any shape and size. Additionally,
while the example implant 10 illustrated in FIGS. 1A and 1B has a circular perimeter
shape defined by the peripheral edge 32, the implant 10 may have an oval shape, a
polygonal shape, a non-polygonal shape, or the like.
[0015] According to aspects of the present disclosure, the back surface 14 of the implant
10 may be shaped to have a surface profile that generally corresponds to a surface
profile of an implantation site of a patient's cornea, and the front surface 12 of
the implant 10 may be shaped to have a surface profile that provides a predetermined
refractive correction. To achieve this, the implant 10 may be precisely custom formed
for the patient receiving the implant 10.
[0016] FIG. 2 illustrates an example procedure 100 for implantation of the implant 10 according
to aspects of the present disclosure. In step 105, a flap is formed in a cornea 16.
For example, a laser (e.g., a femtosecond laser), a mechanical keratome, other cutting
mechanisms (e.g., a blade), etc., may be used to cut the flap. In some embodiments,
the flap may be as thin as flaps that are cut for Sub-Bowman's Keratomileusis. The
flap is sufficiently large to provide stability and ease of handling. In step 110,
the flap of corneal tissue is lifted to expose the corneal interior 18. Thus, as a
result of step 105 and step 110, an anterior portion 20 of the cornea 16 is separated
from a posterior portion 22 of the cornea 16 to expose a stromal bed 24 upon which
the implant 10 can be implanted.
[0017] In step 115, the implant 10 formed from donor corneal tissue is placed onto the stromal
bed 24 at an implantation site in the exposed interior area 18 of the cornea 16 formed
in step 105. The back surface 14 of the implant 10 is placed into contact with the
bed 24 and may have a shape that corresponds to the shape of the bed 24 at the implantation
site. In some cases, the back surface 14 of the implant 10 may have a non-flat surface
curvature that generally corresponds to the non-flat curvature of the bed 24 at the
implantation site. Alternatively, the back surface 14 of the implant 10 may be generally
flat to correspond with a generally flat bed 24 at the implantation site. In some
cases, the flap may have varying thicknesses to combine with the shapes of the implant
10 and the stromal bed 24 to produce the desired corneal shape.
[0018] According to some aspects, the implant 10 is implanted into the cornea 16 in a hydrated
state. In some cases, the implant 10 may be transferred, via an insertion device (not
shown), from a storage media containing the implant 10 prior to the procedure 100
to the implantation site. In other cases, the implant 10 may be transferred from a
controlled environment directly and immediately to the implantation site. For example,
the insertion device may be configured to maintain the implant 10 in the desired hydrated
state. In step 120, the flap is replaced over the implant 10 and corneal interior
18. With the flap in place after step 120, the cornea 16 heals and seals the flap
of corneal tissue to the rest of the cornea 16 (i.e., the anterior portion 20 seals
to the posterior portion 22 to enclose the implant 10).
[0019] As shown in FIG. 3, after the procedure 100, the implant 10 is surgically inserted
within the interior 18 of the cornea 16 with an anterior portion 20 of corneal tissue
16 disposed over the implant 10. Accordingly, in FIGS. 2-3, the implant 10 is implanted
as an inlay implant because it is surgically implanted within the interior 18 of the
cornea 16 (i.e., between the anterior portion 20 and a posterior portion 22 of the
cornea 16). The implant 10 changes the shape of the cornea 16 as evidenced by a change
in the anterior corneal surface 26a, 26b (e.g., in FIG. 3, the anterior corneal surface
is shown as a dashed line 26a prior to the implantation and as a solid line 26b after
implantation). This change in shape of the anterior corneal surface 26a, 26b results
in corrective modification of the cornea 16, e.g., refractive correction, increase
in depth of focus, etc. For example, the implant 10 may address the loss of near vision
associated with presbyopia. To correct the effects of presbyopia, for instance, the
implant 10 may be sized and positioned so that the change to the corneal shape improves
near vision while having minimal effect on distance vision, which requires no correction.
In general, however, the implants 10 may have any size or shape to produce the necessary
desired correction. For instance, in some cases, the implant 10 may have a diameter
of up to approximately 10 mm, but preferably not more than approximately 7 mm.
[0020] In the example procedure 100 illustrated in FIG. 2, the flap of corneal tissue is
formed in step 105 and lifted in step 110 to expose the corneal interior 18, which
receives the implant 10. The flap is then replaced in step 120 over the implant 10.
FIGS. 11A-B illustrate an example implantation of the implant 10 employing a flap
27. The implant 10 has been received into a corneal bed 25 of the cornea 16 and the
flap 27 has been placed over the implant 10. The flap 27 is attached to the rest of
the cornea 16 at a single portion 27a. Meanwhile, the remaining edge 27b of the flap
27 has been incised from the cornea 16 and is not attached to the cornea 16. As such,
when the flap 27 is lifted, the attached portion 27a effectively acts like a hinge.
When the flap 27 is replaced after implant 10 is received by the bed 25, the flap
27 extends over the implant 10 with the attached portion 27a held down against the
rest of the cornea 16. As shown in FIG. 11A, a section 27c of the edge 27b lies opposite
the attached portion 27a. Because the opposing section 27c is not attached to the
cornea 16, it does not lie flat against the cornea 16 in the same manner as the attached
portion 27a. The flap 27 lies over the implant 10 asymmetrically and experiences asymmetric
forces. If this asymmetry remains through healing and sealing of the flap 27 along
the edge 27b, resulting asymmetric stresses on the anterior surface of the cornea
16 may induce an astigmatic shape for the cornea 16.
[0021] To reduce the likelihood of such asymmetric stresses, FIGS. 12A-B illustrate a approach
for forming an alternative flap 27'. Rather than employing a single attached portion
27a as shown in FIGS. 11A-B, the flap 27' includes a plurality of attached portions
27a' that are arranged symmetrically about the flap 27'. As FIGS. 12A-B illustrate,
the flap 27' includes two opposing attached portions 27a', which are both held down
and lie flat against the cornea 16 in a similar manner. Unlike the example of FIGS.
11A-B, the flap 27 lies over the implant 10 symmetrically and experiences symmetric
forces. With such symmetry during healing and sealing of the flap 27' at the unattached
edge 27b', the anterior surface of the cornea 16 is less likely to experience asymmetric
stresses that may induce an astigmatic shape for the cornea 16. In other words, the
opposing attached portions 27a' produce equal and opposite stresses on the anterior
surface of the cornea 16.
[0022] Although the flap 27' is attached at a plurality of areas, the implant 10 can be
received under the flap 27' via the unattached edge 27b'. Although the flap 27' shown
in FIGS. 12A-B includes two attached portions 27a', other embodiments may include
more attached portions 27a'. For instance, the flap 27' may include four attached
portions 27a' arranged symmetrically about the flap 27', i.e., at 0°, 90°, 180°, and
270°. Although the flap 27' may have a circular shape, other embodiments may employ
other shapes, e.g., oval, rectangular, square, etc. In addition, the implant 10 may
also have other shapes, dimensions, etc. In general, the use of symmetrically arranged
attached portions may be used with pockets and other approaches for implanting onlay/inlay
implants to reduce the likelihood of astigmatic effects.
[0023] As described above, the use of implants made from synthetic materials is accompanied
by a variety of disadvantages. In particular, biologic and manufacturing limitations
require synthetic implants to have a significant thickness at their periphery. Due
to this thickness, the corneal tissue disposed over the synthetic implant experiences
a draping effect at the periphery of the implant. This draping effect affects the
shape of the cornea (e.g., at the anterior surface) beyond the periphery of the implant.
In other words, if the synthetic implant has a particular diameter, the effect of
the synthetic implant on the corneal shape is larger than the particular diameter,
i.e., a larger effective zone. To achieve an effective zone for typical corrective
reshaping, the synthetic implant must thus be limited to smaller diameters. For instance,
the synthetic implant may be required to have a diameter of 4 mm or less. It is very
difficult, however, to handle such smaller implants and to align and keep them in
position.
[0024] The implants formed from natural tissue according to the present disclosure do not
have the biologic and manufacturing limitations of synthetic implants and thus do
not experience the same draping effect at their periphery. As such, natural implants
of larger diameters, e.g., greater than 4 mm, may be employed to achieve corrective
reshaping. For a given corneal shape change, the diameter of the natural implant can
be larger than the synthetic implant. The implant procedure does not have to account
for an effective zone that is significantly greater than the diameter of the natural
implant. In some embodiments, the natural implant may have also a skirt that tapers
to near-zero thickness at the periphery to minimize further any possible draping effect.
The corneal tissue is supported by the skirt as the corneal tissue gradually rises
and extends inwardly over the natural implant. With the skirt, the anterior surface
is not affected beyond the periphery of the natural implant, so the corneal shape
change corresponds more predictably to the size of the natural implant. With larger
sizes, the natural implants do not suffer from the disadvantages of the synthetic
implants described above.
[0025] While the implant 10 shown in FIG. 3 is employed as an inlay implant 10, it is understood
that applying the implant 10 to the cornea 16 is not limited to the procedure 100
described above and that other procedures may be employed. For example, rather than
forming a flap, a pocket having side walls with an opening may be formed (e.g., with
a femtosecond laser or other cutting mechanism) to receive the implant 10. Stated
more generally, the cornea 16 can be cut to separate the anterior portion 20 of the
cornea 16 (e.g., the flap or an anterior section of a pocket) from the posterior portion
22 of the cornea 16, exposing the corneal interior 18 upon which the implant 10 can
then be placed at an implantation site and subsequently covered by the anterior portion
20 of the cornea 16.
[0026] In other embodiments, the implant 10 may be employed as an onlay implant, where it
is placed on an outer portion 28 of the cornea 16 just under the epithelium 30 so
that the epithelium 30 can grow over the implant 10. For instance, in an example procedure
300 shown in FIG. 4A, at least a portion of the epithelium 30 is removed (e.g., scraped)
from the cornea 16 in step 305 and the implant 10 is sutured over the outer portion
28 of the corneal tissue 16 in step 310 where the epithelium 30 is allowed to grow
over the implant 10 in step 315.
[0027] Alternatively, in another example procedure 350 shown in FIG. 4B, at least a portion
of the epithelium 30 is removed (e.g., scraped) from the cornea in step 355 and the
implant 10 is stably positioned with an adhesive substance over the outer portion
28 of the corneal tissue 16 in step 360 where the epithelium 30 is allowed to grow
over the implant 10 in step 365. The adhesive substance, for example, may be a synthetic,
biocompatible hydrogel that creates a temporary, soft, and lubricious surface barrier
over the implant 10, keeping the implant 10 in place for the growth of the epithelium
30. According to some aspects of the present disclosure, the adhesive substance can
include a cross-linking agent. In one non-limiting example, the onlay implant 10 can
be dipped into riboflavin to facilitate assist in visualizing placement of the implant
10 on the outer portion 28 of the cornea 16. After placement onto the outer portion
28, the cross-linking agent can be activated (e.g., via a photoactivating light) to
hold the implant 10 to the outer portion 28 of the cornea 16.
[0028] Like the inlay implant, the onlay implant changes the shape of the cornea 16 and
results in corrective modification of the cornea 16. Thus, the onlay implant may be
applied to treat all refractive errors. As shown in FIG. 5, the corneal epithelium
30 grows over the onlay implant 10 which is implanted on the outer portion 28 of the
corneal tissue 16. The epithelium 30 is generally about 50 micrometers (i.e., 5-6
cell layers) thick and generally regenerates when the cornea 16 is damaged or partially
removed. To facilitate recovery after implantation, the shape of the implant 10 is
configured to facilitate the advancement of the epithelium 30 smoothly over the implant
10 during regeneration. More particularly, the implant 10 can have a tapered profile
at the outer peripheral region 37 such that the implant 10 becomes thinner from the
mid-periphery region 36 towards the peripheral edge 32 of the implant 10. Formed from
donor corneal tissue, the implant 10 advantageously promotes effective growth of the
epithelium 30. In addition, the implant 10 provides the accuracy required to achieve
the desired correction.
[0029] As described above, the onlay implant 10 is implanted on an outer portion 28 of the
cornea 16 under the corneal epithelium 30. The Bowman's membrane is a smooth, acellular,
nonregenerating layer, located between the epithelium and the stroma in the cornea
of the eye. It is the outermost layer just below the epithelium. According to some
aspects, the onlay implant 10 may be implanted between the Bowman's membrane and the
epithelium 30. According to additional and/or alternative aspects, the onlay implant
10 may be implanted between one or more cell layers of the epithelium 30. According
to still other additional and/or alternative aspects, the onlay implant 10 may be
implanted such that a minor portion penetrates the Bowman's membrane and/or the stroma
so long as a major portion of the onlay implant 10 is located on or above the Bowman's
membrane and under the outermost layer of the epithelium 30.
[0030] According to one approach, a slight relief (e.g., cavity) is formed in the Bowman's
layer to facilitate positioning of the onlay implant 10 and to help keep the onlay
implant 10 in position during healing. This approach can be employed to lower the
edges of the onlay implant 10, so that epithelial under growth is prevented and the
epithelium 30 can grow more easily over the onlay implant 10.
[0031] During procedures for implanting the implant 10, the cornea may be contained in an
environment that allows the cornea 16 to maintain a state that replicates the state
of a cornea during conventional LASIK procedure, for instance.
[0032] According to another approach, an ultraviolet femtosecond laser is employed to create
a separation between the Bowman's membrane and the epithelium for receiving an implant
and reshaping the cornea. Although infrared femtosecond lasers may be employed to
form pockets in the stroma, such lasers are not suitable for forming the separation
between the Bowman's membrane and the epithelium. The epithelium is approximately
50 µm in thickness and the Bowman's membrane is approximately 8 to 10 µm in thickness.
An infrared femtosecond laser can generate a plasma plume of up to 10 to 20 µm. As
such, if the focus of an infrared femtosecond laser were directed at the surface of
the Bowman's membrane, the Bowman's membrane would be destroyed. If, on the other
hand, the focus of an infrared femtosecond laser were directed high enough into the
epithelium to prevent damage to the Bowman's membrane, epithelium cells would remain
as an undesirable result.
[0033] Meanwhile, an ultraviolet femtosecond laser generates a plasma plume that is only
approximately 2 to 3 µm. As such, with an ultraviolet femtosecond laser, only the
top few microns of the Bowman's membrane can be removed to create the desired separation
between the Bowman's membrane and the epithelium. In some embodiments, monitoring
technologies, such as optical coherence tomography (OCT), may be employed to locate
the Bowman's membrane more accurately and guide the focus of the laser to the appropriate
location. Unlike the present approach which specifically removes (e.g., ablates) a
very thin layer of the Bowman's membrane with technology that has not been heretofore
contemplated for such a use, other approaches employ an infrared femtosecond laser
to create a separation at the cleavage plane and are not directed to the Bowman's
membrane.
[0034] According to yet another approach, a laser is employed to create a pocket within
the epithelium, close to the Bowman's membrane. A cutting instrument can then be inserted
into the pocket to clean/separate the Bowman's membrane layer from the residual epithelium
layers. The pocket is thus prepared to receive an implant.
[0035] According to some aspects of the present disclosure, the implant 10 (i.e., as an
inlay or as an onlay) can be shaped to accommodate a single zone of power for vision
correction. As a non-limiting example, the implant 10 can be shaped primarily to accommodate
near-vision. As another non-limiting example, the implant 10 can be shaped to accommodate
mid-vision or far-vision. According to other aspects of the present disclosure, the
implant 10 can be shaped to provide multi-focality, e.g., accommodate more than one
zone of different power. For example, the implant 10 can include a plurality of different
portions that are each shaped to accommodate a different zone of power. While the
implant 10 illustrated in FIG. 1 is described as having a central region 34, a mid-peripheral
region 36, and an outer peripheral region 37, it should be understood that the implant
10 can have any other number of regions, each having a different power. As one non-limiting
example, the central region 34 of the implant 10 may be shaped to accommodate near-vision,
the mid-peripheral region 36 of the implant 10 may be shaped to accommodate mid-vision,
and/or the outer peripheral region 37 of the implant 10 may be shaped to accommodate
far-vision.
[0036] In general, a single implant 10 may be shaped with varying contours to induce regional
corneal shape changes that treat a combination of disorders. For instance, the implant
10 can be shaped to treat presbyopia in combination with myopia or hyperopia. Indeed,
most people requiring correction for presbyopia are also ametropic. For a patient
with presbyopia and myopia, the implant 10 may have a shape is raised at the periphery
with a cavity/hole in the center, allowing for some steepness in the center of the
cornea. Meanwhile, for a patient with presbyopia and hyperopia, the implant 10 may
have a shape that is convex at the periphery but has a raised center portion.
[0037] In some cases, patients with ectasia or keratoconus, for example, have corneal surface
irregularities. Because their corneas 16 are typically thinner than normal, ablation
techniques cannot be employed to smooth the shape of the corneas 16 to a more regular
shape. To address this problem, a custom implant 10 (i.e., an inlay or an onlay) may
be formed to have a shape that is generally the inverse of the surface irregularity
and thus compensates for the surface irregularity. The implant 10 may be formed to
have a front surface 12 that generally reproduces the back surface 14 curvature. For
example, the implant 10 may be relatively thinner over areas of the cornea 16 that
are relatively higher (i.e., extend outwardly), and vice versa. A non-limiting example
of an onlay implant 10 that having a back surface 14 that is the inverse of the surface
irregularities 38 of the outer portion 28 of the cornea 16 is illustrated in FIG.
6. The implant 10 may even have an aperture 40 that is positioned over steep and high
portions of the cornea 16. For example, FIGS. 7A-7B illustrate a non-limiting example
of an onlay implant 10 having an aperture 40 over a steep and high portion 42 of the
outer portion 28 of the cornea 16. The implant 10 may be implanted as an inlay or
an onlay according to the techniques described above.
[0039] After corneal implantation, the patient may observe a glare and halo caused by the
edge of the implant. In particular, a round edge of the implant may cause a diffractive
(or other optical) effect that produces a round image on the retina. To address a
similar problem with LASIK procedure, a very large optical zone may be employed so
that the halo occurs outside the visual zone. Such a solution, however, cannot be
employed with the implant.
[0040] Accordingly, to minimize the glare and halo effect from an implant, implants according
to the present disclosure may be shaped to have a randomly serrated edge rather than
a smooth round edge. The serrations in the edge may include differently sized peaks,
valleys, etc. As such, the diffractive (or other optical) effect caused by the edge
is diffused and does not create a halo on the retina. Alternatively, to minimize the
glare and halo effect from an implant, the implant may include a predefined edge that
is structured to produce constructive and destructive interference and to manipulate
the focus and depth of field. FIG. 14 illustrates, as a simplified example, an implant
10 with an edge 11 (e.g., randomly serrated) designed to minimize glare and halo effect.
[0041] The implants can be precisely produced according to patient specific conditions.
For instance, the implants of the present disclosure can be manufactured to have a
shape that generally corresponds to a shape of an implantation site of the patient's
cornea, provides a predetermined amount of refractive correction, and/or addresses
corneal irregularities. Approaches for producing eye implants from donor corneal tissue
are described, for instance, in
U.S. Patent Application Publication No. 2014/0264980, filed January 10, 2014, and
U.S. Patent Application Publication No. 2017/0027754, filed February 28, 2016, the contents of these applications being incorporated entirely herein by reference.
[0042] To produce eye implants from a donor cornea, the donor cornea may be delaminated
to form a plurality of laminar sheets. A plurality of lenticules can then be cut from
the laminar sheets and shaped for use as eye implants. The laminar sheets, for instance,
may have a thickness of approximately 10 µm to approximately 50 µm; however, it should
be understood that the laminar sheets can have other thicknesses. As used herein,
the term "laminar sheet" may refer to a sheet that corresponds to a layer of the cornea
defined by the cornea's lamellar structure.
[0043] FIG. 8 illustrates an example delaminating system 500 for delaminating a donor cornea
50. The example system 500 includes a delaminating cutting apparatus 510. The cutting
apparatus 510 includes a light source 512 that generates radiation for dissecting
the tissue 50a of the donor cornea 50 via photodisruption, photothermal cavitation,
laser spallation, etc. The cutting apparatus 510 also includes an optical system 514
that can focus the radiation on the tissue 50a and cut the cornea 50 at a desired
depth d below the anterior surface 50b of the cornea 50. In some embodiments, the
cutting apparatus 510 may generate a femtosecond laser to cut the cornea 50. In addition,
the example system 500 includes a holding device 520 that mechanically positions the
donor cornea 50 to receive the radiation from the cutting apparatus 510.
[0044] The structure of underlying collagen imposes a concave shape on the cornea 50. If
the cornea 50 is compressed and/or experiences other stresses, the cornea 50 may deform
from this concave shape. For instance, in some systems that incise the cornea (e.g.,
ophthalmic surgical systems), an aplanation device is applied to the anterior surface
of the cornea to position the cornea relative to the cutting device. The aplanation
device, for instance, may be formed from glass. When the aplanation device is applied,
the cornea 50 typically flattens. If a cornea is flattened by an aplanation device
and laminar sheets are obtained by cutting the flattened cornea at the predetermined
depth
d, the resulting laminar sheets might not have the desired uniform thicknesses due
to the structure of the underlying collagen. In general, deformation of the cornea
50 may prevent the cutting apparatus 510 from accurately cutting the cornea 50 at
the predetermined depth
d.
[0045] Advantageously, the holding device 520 in FIG. 8 engages the cornea 50 without substantially
deforming the cornea 50. As such, the cutting apparatus 510 can cut laminar sheets
of more uniform thickness from the cornea 50.
[0046] When an aplanation device is employed to flatten the cornea, the aplanation device
can be used as a reference point and the cornea can be cut at a predetermined depth
from the aplanation device to obtain laminar sheets of desired thickness. In addition
to introducing deformation that may affect the accuracy of cutting laminar sheets
of desired thickness, however, an aplanation device may disadvantageously prevent
the entire cornea from being used to form the laminar sheets. In other words, the
aplanation device may not allow laminar sheets to be cut from sections of the cornea
50 extending fully from limbus to limbus.
[0047] In contrast, the example system 500 does not employ an aplanation device, so the
example system 500 can use more of the cornea 50 and produce eye implants from the
cornea 50 more efficiently. In particular, the example system 500 includes a guide
system 530 that can guide the cutting apparatus 510 to cut laminar sheets from limbus
to limbus of the cornea 50.
[0048] With the holding device 520 maintaining the cornea 50 at a fixed distance relative
to the cutting apparatus 510, the guide system 530 can measure a distance
D from the cutting apparatus 510 to the cornea 50, e.g., the surface 50b. The guide
system 530 can communicate this distance measurement to a controller 540 that controls
aspects of the cutting apparatus 510. The distance measurement provides the cutting
apparatus 510 with the necessary reference to align and focus the femtosecond laser
at a desired depth within the corneal tissue 50a. The femtosecond laser spot can be
scanned over the cornea 50 to focus on points at the desired depth within the corneal
tissue 50a to cut a laminar sheet extending fully from limbus to limbus. Unlike other
systems, an aplanation device is not required in the example system 500 to provide
a reference to determine focus depth for the femtosecond laser. Advantageously, by
cutting the cornea 50 in this way, the concave contour of the posterior surface of
the laminar sheet is also known/controlled for subsequent processing.
[0049] Although the optical system 520 can move the femtosecond laser over a stationary
cornea 50, the holding device 520 in alternative embodiments can move the cornea 50
relative to a stationary irradiation system 520 (similar, for instance, to the operation
of a goniometer stage), while the femtosecond laser cuts the cornea 50. In general,
relative movement between the cornea 50 and the cutting apparatus 510 is guided by
the guide system 530 to align and focus the femtosecond laser to the appropriate positions
in the corneal tissue 50a to delaminate the cornea 50 at the predetermined depth
d.
[0050] The example system 500 may also include a deformation monitoring system 550 that
can measure any deformation of the cornea 50 that may occur while the cutting apparatus
510 cuts the cornea 50. For instance, the monitoring system 540 may employ second
harmonic imaging, autofluorescence imaging, Brillouin scattering measurement, and/or
x-ray scattering measurement before and during the cutting process to determine any
deformation. If necessary, the optical system 514 can be adjusted to account for the
deformation and allow the cornea 50 to be cut more accurately at the predetermined
depth
d. For instance, the focal depth of a femtosecond laser generated by the illumination
system 510 can be adjusted to cut the cornea 50 with the desired thickness. The deformation
monitoring system 550 can communicate the deformation measurement to the controller
540 which controls aspects of the cutting apparatus 510.
[0051] According to an example embodiment, the cutting apparatus 510 may apply a femtosecond
laser also to induce gas bubbles at particular locations in the tissue 50a. The gas
bubbles provide markers that can be monitored with the monitoring system 540. Movement
of the gas bubbles can be measured to determine a deformation of the cornea 50.
[0052] Although the example system 500 may employ the holding device 520 which does not
deform the cornea 50, aspects of the deformation monitoring system 540 may be employed
in systems that employ an aplanation device. Such systems can then make necessary
corrections to cut the cornea accurately at desired depths even with the deformation
induced by the aplanation device.
[0053] FIG. 13A illustrates an example system 800 for forming a plurality of lenticules
60 from a donor cornea 50. The system 800 includes a first cutting apparatus 810 that
can cut the donor cornea 50 to form a portion 52 of corneal tissue. The donor cornea
50 includes an anterior surface and a posterior surface. The first cutting apparatus
810 can cut the donor cornea 50 along an axis extending between the anterior surface
and the posterior surface as illustrated in FIG. 13A.
[0054] After operation of the first cutting apparatus 810, the portion 52 of corneal tissue,
for instance, may be substantially cylindrical in shape. As used herein, the term
"cylindrical" indicates a three-dimensional shape that extends along an axis between
two ends and has a substantially uniform circular cross-section transverse to the
axis from one end to the other; the surfaces at the two ends are not necessarily planar
and may be contoured (e.g., convex, concave, etc.).
[0055] According to one embodiment, the first cutting apparatus 810 may include a femtosecond
laser. Alternatively, the first cutting apparatus 810 may include a single blade that
is operable to move along the axis and cut the donor cornea 50 from the anterior surface
to the posterior surface, where the blade has a shape that defines a cross-section
transverse to the axis. For instance, the blade may be substantially cylindrical so
that the portion 52 of corneal tissue is correspondingly substantially cylindrical
in shape. In effect, the blade may punch the donor cornea 50 to produce the portion
52 of corneal tissue. Alternatively, the first cutting apparatus 810 may include more
than one blade that can be applied to the donor cornea 50 in any number of steps to
produce three-dimensionally the portion 52 of corneal tissue.
[0056] The system 800 also includes a second cutting apparatus 820 that can make a series
of cuts transverse to the axis. As such, the second cutting apparatus 810 can form
a plurality of lenticules 60 from the portion 52 of corneal tissue. The corneal tissue
between consecutive cuts by the second cutting apparatus 810 provides a corresponding
lenticule 60 to be shaped for a corneal implant. The distance between the consecutive
cuts defines a thickness for the corresponding lenticule 60. According to one embodiment,
the second cutting apparatus 810 may include an ultraviolet femtosecond laser, which
provides the advantages described herein.
[0057] The consecutive cuts made by the second cutting apparatus 820 include a first cut
made closest to the anterior surface of the donor cornea 50 and a second cut made
closest to the posterior surface of the donor cornea 50. Thus, the corresponding lenticule
60 includes a first surface formed by the first cut and a second surface formed by
the second cut. In some embodiments, the second cutting apparatus 820, e.g., including
an ultraviolet femtosecond laser, may shape at least one of the first surface or the
second surface of the corresponding lenticule 60 to form an corneal implant with a
desired refractive profile.
[0058] The donor cornea 50 may include a plurality of lamellar layers disposed between the
anterior surface and the posterior surface, where the lamellar layers are formed by
the lamellae in the corneal tissue. The first cutting apparatus 810 may cut the donor
cornea 50 transversely through the lamellar layers, while the second cutting apparatus
820 can make cuts along the lamellar layers.
[0059] FIG. 13B illustrates an embodiment 800' of the example system 800 for forming a plurality
of lenticules 60 from a donor cornea 50. In particular, the cornea 50 is cut to provide
a cylinder 52' of corneal tissue with a pre-determined diameter. The corneal tissue
cylinder 52' is frozen, and the second cutting apparatus 810 may be a cryo-microtome
820' (freezing microtome, microtome-cryostat, or the like) that slices the frozen
corneal tissue cylinder 54 into a plurality of lenticules 60 of desired thickness(es).
A cryo-microtome may generally involve the use of a microtome in a temperature-regulated
chamber. For instance, a rotary microtome can be adapted to cut in a liquid-nitrogen
chamber 830, where the reduced temperature increases the hardness of the corneal tissue
cylinder 52' to facilitate the preparation of thin lenticules 60. The temperature
of the corneal tissue cylinder 52' of corneal tissue and the second cutting apparatus
may be controlled to achieve the desired lenticule thickness(es).
[0060] In some cases, a plurality of corneal tissue cylinders 52' may be cut from the donor
cornea 50. Taking the desired diameters for the corneal tissue cylinders 52' into
account, the locations of the sections of the cornea 50 from which the respective
corneal tissue cylinders 52' are cut can be positioned (e.g., mathematically determined)
so that as much of the cornea 50 as possible is used to provide the lenticules 60.
In other words, waste of the donor cornea 50 is minimized and the greatest possible
number of lenticules 60 is obtained from the given donor cornea 50.
[0061] Furthermore, to obtain the greatest possible number of lenticules 60 from the given
cornea 50, the cryo-microtome 820' may slice the lenticules 60 from the frozen corneal
tissue cylinders 54 such that each lenticule 60 has a thickness that is slightly greater
than the maximum thickness required for the desired application for the lenticule
60. For instance, the lenticule 60 may be shaped to form an implant with a particular
thickness profile to provide a refractive correction of a particular diopter. The
thickness of the lenticule 60 is sufficient to achieve this thickness profile while
also minimizing waste during the shaping of the implant. In one example, an implant
is shaped from the lenticule 60 with a certain central thickness to correct four diopter
hyperopia. If another implant is shaped to correct five diopter hyperopia, the corresponding
lenticule 60 would have a thickness that is greater by an amount equal to the difference
of the four diopter implant and the five diopter implant. Because the cryo-microtome
820' has a cutting resolution down to the micron level, the approach 800' advantageously
provides for efficient use of the donor cornea 50 not possible with any other approach.
[0062] As described above with reference to FIG. 13A, the first cutting apparatus 810 may
include a substantially cylindrical blade that cuts the donor cornea 50 so that the
portion 52 of corneal tissue is correspondingly substantially cylindrical in shape.
FIG. 13C illustrates an example system 800", where the cylindrical blade 810" is configured
to produce and hold a cylinder 52" of corneal tissue as the second cutting apparatus
820" makes a series of cuts to the corneal tissue cylinder 52". The second cutting
apparatus 820" may be an ultraviolet femtosecond laser with a high numerical aperture
(NA), e.g., greater than 0.8.
[0063] The system 800" may include a source of hydration fluid 840, and the cylindrical
blade 810" can be immersed in the source of hydration fluid 840 while holding the
corneal tissue cylinder 52". As such, the hydration fluid 840 keeps the corneal tissue
cylinder 52" hydrated while the second cutting apparatus 820" cuts the portion of
corneal tissue. The cylindrical blade 810" may include apertures or the like to allow
the hydration fluid 840 into cylindrical blade 810" into contact with the corneal
tissue cylinder 52". The temperature of the hydration fluid 840 can also be controlled
to keep the corneal tissue cylinder 52" at a proper temperature.
[0064] The system 800" may additionally include a cutting stage 850. The cylindrical blade
810" is configured to be mounted on the cutting stage 850 as the second cutting apparatus
820" makes the series of cuts to the corneal tissue cylinder 52". The cuts are made
at least along the x-y plane as shown in FIG. 13C. A first end 810a" (e.g., bottom)
of the cylindrical blade 810" is positioned on, or otherwise engaged by, the cutting
stage 850, and the second cutting apparatus 820" is positioned to make the series
of cuts at a second opposing end 810b" of (e.g., above) the cylindrical blade 810".
[0065] The system 800" may include a guide system 860 that determines the position of the
corneal tissue cylinder 52" for the second cutting apparatus 820". For instance, the
guide system 840 may be an optical system that provides image or other data to a controller
that can determine the position of the corneal tissue cylinder 52" from the data and
control the operation of the second cutting apparatus 820".
[0066] The cutting stage 830 may include an actuator 852, such as a piezoelectric actuator
or similar electromechanical device, that contacts the corneal tissue cylinder 52"
at the first end 810a" of the cylindrical blade 810" and moves (e.g., pushes) the
corneal tissue cylinder 52" through the cylindrical blade 810" toward the second end
810b" as the second cutting apparatus 820" makes the series of cuts to the corneal
tissue cylinder 52".
[0067] Consecutive cuts made by the second cutting apparatus 820" include a first cut made
closest to the anterior surface of the donor cornea 50 and a second cut made closest
to the posterior surface of the donor cornea 50. The consecutive cuts form a corresponding
lenticule 60 that includes a first surface formed by the first cut and a second surface
formed by the second cut. The second cutting apparatus 820" may also shape at least
one of the first surface or the second surface of the corresponding lenticule 60 to
form the corneal implant with a desired refractive profile.
[0068] For instance, if the second cutting apparatus 820" is an ultraviolet femtosecond
laser, the ultraviolet femtosecond laser can shape (e.g., sculpt) the most anterior
(e.g., top) surface of the corneal tissue cylinder 52" along the x-, y-, z-axes according
to a desired refractive profile. According to one approach, the laser spot of the
ultraviolet femtosecond laser may be kept fixed in space and the cutting stage 850
may be operated to move along the x-, y-, z-axes relative to the laser spot. According
to another approach, the laser of the ultraviolet femtosecond laser scans the corneal
tissue cylinder 52" along the x-, y- , z-axes. The first surface of a lenticule 60
is formed when the most anterior surface is shaped. The ultraviolet femtosecond laser
then makes a second cut to form the second surface of the lenticule 60 and release
the lenticule 60 from the corneal tissue cylinder 52". The second surface may be planar
or contoured (e.g., concave). In general, the lenticule 60 may have any size or shape
according to the desired refractive profile. Once the second surface is cut, the actuator
852 can move the corneal tissue cylinder 52" toward the second end 510b" (e.g., upwardly)
and push the lenticule 60 out of the cylindrical blade 510".
[0069] The system 800" may also include a robotic arm 870 that retrieves each lenticule
60 as it is formed by the second cutting apparatus 810 and pushed out of the cylindrical
blade 510" by the actuator 852. The robotic arm 870 may apply a negative pressure
to the lenticule 60 to hold the lenticule 60 by suction. The robotic arm 870 may transport
the lenticule 60 for further processing, such as measurement and/or packaging.
[0070] Although the system 800" may demonstrate how the second cutting apparatus 820 can
cut the portion 52 of corneal tissue held by the first cutting apparatus 810. Other
approaches are possible. For instance, a cylindrical blade can hold the portion 52
of corneal tissue and a ultraviolet femtosecond laser can make a series of cuts starting
from the most posterior surface of the portion 52 of corneal tissue and proceeding
toward the most anterior surface (e.g., working from bottom to top). Such an approach
may produce meniscus-shaped lenses in particular, but other shapes are possible. When
the series of cuts by the ultraviolet femtosecond laser is completed, the portion
52 of corneal tissue can be pushed through the cylindrical blade to produce a "pile"
of lenticules 60.
[0072] FIG. 10 illustrates an example approach 700 for shaping a lenticule to achieve a
desired corneal implant. Laminar sheets may be cut from donor tissue 50 as described
above. In particular, a delaminating cutting apparatus 710 includes a light source
712 that generates radiation for dissecting tissue 50a of the donor cornea 50 via
photodisruption, photothermal cavitation, laser spallation, etc. The cutting apparatus
710 also includes an optical system 714 that can focus the radiation on the tissue
50a and cut the cornea 50 at a desired depth d below the anterior surface 50b of the
cornea 50. In some embodiments, the cutting apparatus 710 may generate a femtosecond
laser to cut the cornea 50.
[0073] As shown in FIG. 10, lenticules 60 are then cut from the laminar sheets with varying
sizes. For instance, from a laminar sheet 70a, two lenticules 60a are cut with a size
that can be used to form implants 10a for treating presbyopia, and one lenticule 60b
is cut with a size that can be used to form implants 10b for treating hyperopia. If
three laminar sheets 70a can be cut from the donor cornea 50, six presbyopia lenticules
60a and three hyperopia lenticules 60b can be obtained from the cornea 50. Additionally
or alternatively, from a laminar sheet 70b, six presbyopia lenticules 60a are cut,
and with three such laminar sheets 70b, eighteen presbyopia lenticules 60a can be
obtained from the cornea 50.
[0074] A holding system 730 mechanically positions a lenticule 60 to receive shaping (e.g.,
ablative) radiation from an implant shaping apparatus 740. The holding system 730
includes a lower structure 732 and an upper structure 734. The lower structure 732
has a round (e.g., circular) upper surface 732a that receives the lenticule 60. The
upper structure 734 has a rectangular lower surface 734a that holds (e.g., fixes)
the lenticule 60 in position on the lower structure 732. The rectangular shape allows
the upper structure 734 to engage the lenticule 60. The width (e.g., diameter) of
the upper surface 732a of the lower structure 732 may be substantially equal to an
edge length of the lower surface 734a of the upper structure 734. The lower structure
732 includes a round (e.g., circular) aperture 732b and the upper structure 734 includes
a corresponding round (e.g., circular) aperture 734b. The apertures 732b, 734b allow
the implant shaping apparatus 740 to shape the lenticule 60 between the lower structure
732 and the upper structure 734.
[0075] According to some approaches, a lenticule may be prepared and packaged (e.g., by
a supplier) for delivery and subsequent reshaping (e.g., by a practitioner) at or
near the time of actual implantation into the cornea. As such, the lenticule may provide
a more general shape (e.g., a blank) that can be subsequently reshaped into an implant
according to any specific shape. As described above, the specific shape may cause
a change in refractive power when implanted. In addition, the shape may include desired
edge characteristics and other features that allow the structure of the implant to
blend or transition smoothly into the surrounding eye structure, for instance, to
improve optics and/or promote epithelial growth over the implant.
[0076] If a separate supplier packages and delivers a lenticule as a blank to a practitioner,
the practitioner may need to know the starting measurements of the lenticule so that
the proper amount of tissue can be accurately removed from the lenticule to obtain
a precisely shaped corneal implant. In some approaches, the supplier may take the
measurements of the lenticule prior to packaging and may provide the measurements
to the practitioner. Additionally, the supplier may provide instructions that the
practitioner can follow to reshape the lenticule in order to obtain a particular shape
for the implant. For instance, the instructions may indicate what tissue should be
removed from particular locations of the lenticule. Such instructions are based on
the measurements taken of the lenticule.
[0077] Where a lenticule is delivered as a blank to a practitioner, the practitioner may
subsequently employ a reshaping system to reshape the lenticule. FIG. 9 illustrates
an example reshaping system 600 that allows a lenticule 60 to be reshaped in a controlled
environment. As shown in FIG. 9, the reshaping system 600 includes a lenticule cutting
apparatus 610. The cutting apparatus 610 may include a laser source 612 that emits
a laser, such as an excimer laser, capable of cutting corneal tissue. The cutting
apparatus 610 may also include one or more optical elements 614 that direct the laser
from the laser source. Such optical elements 614 may include any combination of lenses,
mirrors, filters, beam splitters, etc.
[0078] The example reshaping system 600 includes a staging device 630 that stages the lenticule
60 for reshaping by the cutting apparatus 610, while keeping the lenticule 60 in a
proper state (e.g., hydration, temperature, etc.). As shown in FIG. 9, the staging
device 630 includes a container 632. The container 632 includes a chamber 632a, an
upper opening 632b, and a lower opening 632c. The staging device 630 also includes
a cover 634 to cover the upper opening 632b via threaded engagement, friction fit,
clamps, or the like.
[0079] The staging device 630 includes a plunger 636 that passes through the lower opening
632c into the chamber 632a. The plunger 636 includes an upper end 636a and a lower
end 636b. The upper end 636a is disposed in the chamber 632a while the lower end 636b
is accessible outside the chamber 632a from the bottom of the container 632. Pressure
applied against the lower end 636b causes the plunger 636 to move farther through
the lower opening 632c and into the chamber 632a. In effect, this pressure raises
the upper end 636a within the chamber 632a.
[0080] Conversely, the lower end 636b can be pulled away from the container 632 to retract
the plunger 636 from the chamber 632a. In effect, this action lowers the upper end
636a within the chamber 632a.
[0081] In some embodiments, the plunger 636 can be manually operated. In other embodiments,
the plunger 636 may be actuated by a machine, e.g., electro-mechanical device.
[0082] The staging device 630 includes a holder 638 that is configured to hold the lenticule
60. The upper end 636a of the plunger 636 is configured to receive the holder 638.
According to one approach, a supplier can pack the lenticule 60 in the holder 638
for delivery to the practitioner. As delivered, holder 638 facilitates handling of
the lenticule 60. In particular, the lenticule 60 is already properly oriented in
the holder 632 (e.g., with the correct surface facing up) for subsequent reshaping
with the cutting apparatus 610.
[0083] In operation, the cover 634 is removed from the upper opening 632b and the holder
638 with the lenticule 60 is positioned on the upper end 636a of the plunger 636.
The chamber 632a is then filled to a predetermined level with hydrating fluid, e.g.,
balanced salt solution (BSS) or other standardized salt solution, to maintain the
lenticule 60 in a hydrated state. The plunger 636 is positioned so that the lenticule
60 is submerged in the hydrating fluid. A liquid-tight seal is provided around the
plunger 636 at the lower opening 632c so that liquid can be contained in the chamber
632a without escaping through the lower opening 632c. The cover 634 is then secured
over the upper opening 632b of the container 632. Accordingly, the container 634 provides
an enclosure in which the lenticule 60 can be reshaped in a controlled environment
by the cutting apparatus 610.
[0084] The cover 634 includes a window 634a that allows the cutting apparatus 610 to direct
a laser into the chamber 632a to cut the lenticule 60 while the holder 638 with the
lenticule 60 is disposed on the upper end 636a of the plunger 636. For instance, the
window 634d may be formed from quartz that allows transmission of ultraviolet light,
e.g., light having a wavelength equal to approximately 193 nm.
[0085] In further operation, when the cutting apparatus 610 is aligned with the container
632 to reshape the lenticule 60, pressure can be applied to the lower end 636b of
the plunger 636 to raise the holder 638 on the upper end 636a within the chamber 632a.
The container 632 also includes one or more stops 632d that stop the plunger 636 from
advancing beyond a predetermined distance within the chamber 632a. In particular,
when the plunger 636 advances to the stops 632d, the lenticule 60 moves above the
predetermined level of hydrating fluid to allow the laser from the cutting apparatus
610 to act on the lenticule 60. The posterior surface of the lenticule 60, however,
may remain in contact with the hydrating fluid to maintain hydration. Indeed, the
holder 638 may include an aperture 638a to promote contact between the lenticule 60
and the hydrating fluid. As shown in FIG. 9, the plunger 636 abuts the stops 632d
and the lenticule 60 is raised above the predetermined fluid level; from this position,
the plunger 636 can be retracted to submerge the lenticule 60 in the hydrating fluid.
[0086] The staging device 630 also includes an air supply 640 that can deliver filtered
air into the chamber 632a. Once the lenticule 60 is above the predetermined level
of hydrating fluid, the air supply 640 can blow filtered air toward the lenticule
60 to dry and clean the lenticule 60 sufficiently for the reshaping process. Furthermore,
as the cutting apparatus 610 reshapes the lenticule 60, the air supply 640 can continue
to blow the filtered air to remove any ablation plume. The air supply 640 can deliver
the air toward the lenticule 60 while avoiding direct air flow which may cause dehydration.
After the lenticule 60 is reshaped, the plunger 636 can be retracted to draw the lenticule
60 back into the hydrating fluid.
[0087] The staging device 630 may also include a heating element 650 that can control the
temperature of the hydrating fluid. For instance, the temperature of the hydrating
fluid may be raised to 37°C, which maintains the lenticule 60 at physiological temperature
and provides humidity within the enclosure of the chamber 632a. For instance, the
heating element 650 may be a small resistive coil, e.g., formed from Nichrome, and
the temperature may be controlled by a thermistor.
[0088] The hydrating fluid may also maintain an isotonic state for the lenticule 60. In
vivo, the cornea does not maintain an isotonic thickness, as the corneal endothelial
pumps are continually working to dehydrate the cornea slightly. As such, the thickness
of the corneal tissue in vivo may be a slightly smaller than what its thickness would
be in an isotonic solution. Therefore, when cutting the lenticule 60, the reshaping
system 600 may take into account that the implant 10 sculpted from the lenticule 60
may become thinner after it is implanted in the recipient eye.
[0089] In general, the reshaping system 600 provides an example of a system for forming
a corneal implant, where a receptacle (e.g., container 632) receives a lenticule and
maintains a state (e.g., hydration, temperature, etc.) of the lenticule. The receptacle
provides a controlled environment for precise and predictable cutting by a cutting
apparatus. For instance, the per-pulse cutting rate for a laser may be sensitive to
hydration of the lenticule 60, so the lenticule 60 may need to be predictably hydrated
for precise and accurate sculpting.
[0090] The reshaping system 600 also includes a controller 660, which may be implemented
with at least one processor, at least one data storage device, etc., as described
further below. The controller 660 is configured to determine a sculpting plan for
modifying a first shape of the lenticule 60 and achieving a second shape for the lenticule
60 to produce the implant 10 with the desired refractive profile. The controller 660
can control the cutting apparatus 610 to direct, via the one or more optical elements
614, the laser from the laser source 612 to sculpt the lenticule 60 according to the
sculpting plan to produce the implant 10. A monitoring system (not shown) may be employed
to guide the laser relative to the position of the lenticule 60. In some cases, the
lenticule 60 may be reshaped in relation to predicted corneal biomechanical changes
based on the depth of the implant within the cornea. Additionally or alternatively,
the lenticule 60 may be reshaped in relation to predicted epithelium changes based
on the deformation of the anterior stroma.
[0092] According to aspects of the present disclosure, some or all of the steps of the above-described
and illustrated procedures can be automated or guided under the control of a controller.
Generally, the controllers may be implemented as a combination of hardware and software
elements. The hardware aspects may include combinations of operatively coupled hardware
components including microprocessors, logical circuitry, communication/networking
ports, digital filters, memory, or logical circuitry. The controller may be adapted
to perform operations specified by a computer-executable code, which may be stored
on a computer readable medium.
[0093] As described above, the controller may be a programmable processing device, such
as an external conventional computer or an on-board field programmable gate array
(FPGA) or digital signal processor (DSP), that executes software, or stored instructions.
In general, physical processors and/or machines employed by embodiments of the present
disclosure for any processing or evaluation may include one or more networked or non-networked
general purpose computer systems, microprocessors, field programmable gate arrays
(FPGA's), digital signal processors (DSP's), micro-controllers, and the like, programmed
according to the teachings of the exemplary embodiments of the present disclosure,
as is appreciated by those skilled in the computer and software arts. The physical
processors and/or machines may be externally networked with the image capture device(s),
or may be integrated to reside within the image capture device. Appropriate software
can be readily prepared by programmers of ordinary skill based on the teachings of
the exemplary embodiments, as is appreciated by those skilled in the software art.
In addition, the devices and subsystems of the exemplary embodiments can be implemented
by the preparation of application-specific integrated circuits or by interconnecting
an appropriate network of conventional component circuits, as is appreciated by those
skilled in the electrical art(s). Thus, the exemplary embodiments are not limited
to any specific combination of hardware circuitry and/or software.
[0094] Stored on any one or on a combination of computer readable media, the exemplary embodiments
of the present disclosure may include software for controlling the devices and subsystems
of the exemplary embodiments, for driving the devices and subsystems of the exemplary
embodiments, for enabling the devices and subsystems of the exemplary embodiments
to interact with a human user, and the like. Such software can include, but is not
limited to, device drivers, firmware, operating systems, development tools, applications
software, and the like. Such computer readable media further can include the computer
program product of an embodiment of the present disclosure for performing all or a
portion (if processing is distributed) of the processing performed in implementations.
Computer code devices of the exemplary embodiments of the present disclosure can include
any suitable interpretable or executable code mechanism, including but not limited
to scripts, interpretable programs, dynamic link libraries (DLLs), Java classes and
applets, complete executable programs, and the like. Moreover, parts of the processing
of the exemplary embodiments of the present disclosure can be distributed for better
performance, reliability, cost, and the like.
[0095] Common forms of computer-readable media may include, for example, a floppy disk,
a flexible disk, hard disk, magnetic tape, any other suitable magnetic medium, a CD-ROM,
CDRW, DVD, any other suitable optical medium, punch cards, paper tape, optical mark
sheets, any other suitable physical medium with patterns of holes or other optically
recognizable indicia, a RAM, a PROM, an EPROM, a FLASH-EPROM, any other suitable memory
chip or cartridge, a carrier wave or any other suitable medium from which a computer
can read.
[0096] While the present disclosure has been described with reference to one or more particular
embodiments, those skilled in the art will recognize that many changes may be made
thereto without departing from the spirit and scope of the present disclosure. Each
of these embodiments and obvious variations thereof is contemplated as falling within
the spirit and scope of the invention. It is also contemplated that additional embodiments
according to aspects of the present disclosure may combine any number of features
from any of the embodiments described herein.
[0097] The following numbered paragraphs (paras.) which form part of the description contain
further statements of various aspects of the present invention:-
- 1. A system for forming corneal implants, comprising:
a first cutting apparatus configured to cut a donor cornea and form a portion of corneal
tissue, wherein the donor cornea includes an anterior surface and a posterior surface,
the first cutting apparatus configured to cut the donor cornea along an axis extending
between the anterior surface and the posterior surface; and
a second cutting apparatus configured to form a plurality of lenticules from the portion
of corneal tissue by making, to the portion of corneal tissue, a series of cuts transverse
to the axis, wherein corneal tissue between consecutive cuts by the second cutting
apparatus provides a corresponding lenticule to be shaped for a corneal implant, a
distance between the consecutive cuts defining a thickness for the corresponding lenticule.
- 2. The system of para 1, further comprising a temperature-regulated chamber configured
to maintain the portion of corneal tissue at a low temperature for cutting of the
portion of corneal tissue by the second cutting apparatus.
- 3. The system of para 1, wherein the second cutting apparatus includes a cryo-microtome.
- 4. The system of para 1, wherein the first cutting apparatus includes a femtosecond
laser.
- 5. The system of para 1, wherein the second cutting apparatus includes an ultraviolet
femtosecond laser.
- 6. The system of para 1, wherein the consecutive cuts made by the second cutting apparatus
include a first cut made closest to the anterior surface of the donor cornea and a
second cut made closest to the posterior surface of the donor cornea, the corresponding
lenticule including a first surface formed by the first cut and a second surface formed
by the second cut, and the second cutting apparatus is further configured to shape
at least one of the first surface or the second surface of the corresponding lenticule
to form the corneal implant with a desired refractive profile.
- 7. The system of para 1, wherein the first cutting apparatus includes a blade operable
to move along the axis and cut the donor cornea from the anterior surface to the posterior
surface, the blade having a shape that defines a cross-section transverse to the axis
for the portion of corneal tissue.
- 8. The system of para 7, wherein the blade is substantially cylindrical and is operable
to provide the portion of corneal tissue with a substantially circular cross-section
transverse to the axis.
- 9. The system of para 8, wherein the cylindrical blade is configured to hold the portion
of corneal tissue as the second cutting apparatus makes the series of cuts to the
portion of corneal tissue.
- 10. The system of para 9, further comprising a source of hydration fluid, wherein
the cylindrical blade is configured to be immersed in the source of hydration fluid
while holding the portion of corneal tissue, the hydration fluid keeping the portion
of corneal tissue hydrated while the second cutting apparatus cuts the portion of
corneal tissue.
- 11. The system of para 9, further comprising a cutting stage, wherein the cylindrical
blade is configured to be mounted on the cutting stage as the second cutting apparatus
makes the series of cuts to the portion of corneal tissue.
- 12. The system of para 11, wherein the second cutting apparatus includes a femtosecond
laser, wherein a first end of the cylindrical blade is positioned at the cutting stage,
and the second cutting apparatus is positioned to make the series of cuts at a second
opposing end of the cylindrical blade.
- 13. The system of para 12, further comprising a detection system configured to determine
the position of the portion of corneal tissue for the second cutting apparatus.
- 14. The system of para 12, wherein the consecutive cuts made by the femtosecond laser
include a first cut made closest to the anterior surface of the donor cornea and a
second cut made closest to the posterior surface of the donor cornea, the corresponding
lenticule including a first surface formed by the first cut and a second surface formed
by the second cut, and the femtosecond laser is configured to shape at least one of
the first surface or the second surface of the corresponding lenticule to form the
corneal implant with a desired refractive profile.
- 15. The system of para 12, wherein the cutting stage includes an actuator configured
to contact the portion of corneal tissue at the first end of the cylindrical blade
and move the portion of corneal tissue through the cylindrical blade toward the second
end as the second cutting apparatus makes the series of cuts to the portion of the
corneal tissue.
- 16. The system of para 14, further comprising a robotic arm configured to retrieve
each corresponding lenticule as the second cutting apparatus makes the consecutive
cuts and the actuator moves the portion of corneal tissue through the cylindrical
blade.
- 17. The system of para 1, wherein the portion of corneal tissue has a substantially
circular cross-section transverse to the axis, and each lenticule has a substantially
circular perimeter.
- 18. A method for forming corneal implants, comprising:
providing a donor cornea including an anterior surface and a posterior surface;
forming, with a first cutting apparatus, a portion of corneal tissue by cutting the
donor cornea along an axis extending between the anterior surface and the posterior
surface; and
forming, with a second cutting apparatus, a plurality of lenticules from the portion
of corneal tissue by making, to the portion of corneal tissue, a series of cuts transverse
to the axis, wherein corneal tissue between consecutive cuts by the second cutting
apparatus provides a corresponding lenticule to be shaped for a corneal implant, a
distance between the consecutive cuts defining a thickness for the corresponding lenticule.
- 19. The method of para 18, further comprising freezing the portion of corneal tissue,
wherein the second cutting apparatus includes a cryo-microtome configured to cut the
frozen portion of corneal tissue.
- 20. The method of para 18, wherein the consecutive cuts made by the second cutting
apparatus include a first cut made closest to the anterior surface of the donor cornea
and a second cut made closest to the posterior surface of the donor cornea, the corresponding
lenticule including a first surface formed by the first cut and a second surface formed
by the second cut, and the method further comprises shaping, with the second cutting
apparatus, at least one of the first surface or the second surface of the corresponding
lenticule to form the corneal implant with a desired refractive profile.
1. A system (800, 800', 800") for forming corneal implants (10), comprising:
a first cutting apparatus (810, 810") configured to cut a donor cornea (50) and form
a portion (52, 52', 52", 54) of corneal tissue, wherein the donor cornea includes
an anterior surface and a posterior surface, the first cutting apparatus configured
to cut the donor cornea along an axis extending between the anterior surface and the
posterior surface; and
a second cutting apparatus (820, 820', 820") configured to form a plurality of lenticules
(60) from the portion (52, 52', 52", 54) of corneal tissue by making, to the portion
of corneal tissue, a series of cuts transverse to the axis, wherein corneal tissue
between consecutive cuts by the second cutting apparatus provides a corresponding
lenticule to be shaped for a corneal implant (10), a distance between the consecutive
cuts defining a thickness for the corresponding lenticule.
2. The system of claim 1, further comprising a temperature-regulated chamber (830) configured
to maintain the portion of corneal tissue (52, 52', 52", 54) at a low temperature
for cutting of the portion of corneal tissue by the second cutting apparatus (820,
820', 820").
3. The system (900, 800') of claim 1, wherein the first cutting apparatus (810) includes
a femtosecond laser, or wherein the second cutting apparatus (820) includes a cryo-microtome
(820') or an ultraviolet femtosecond laser (820").
4. The system (800, 800', 800") of claim 1, wherein the consecutive cuts made by the
second cutting apparatus (820, 820', 820") include a first cut made closest to the
anterior surface of the donor cornea (50) and a second cut made closest to the posterior
surface of the donor cornea, the corresponding lenticule (60) including a first surface
formed by the first cut and a second surface formed by the second cut, and the second
cutting apparatus (820, 820', 820") is further configured to shape at least one of
the first surface or the second surface of the corresponding lenticule (60) to form
the corneal implant (10) with a desired refractive profile.
5. The system (800, 800', 800") of claim 1, wherein the first cutting apparatus (810)
includes a blade (810") operable to move along the axis and cut the donor cornea (50)
from the anterior surface to the posterior surface, the blade (810") having a shape
that defines a cross-section transverse to the axis for the portion (52, 52', 52",
54) of corneal tissue.
6. The system (800, 800', 800") of claim 5, wherein the blade (810") is substantially
cylindrical and is operable to provide the portion (52, 52', 52", 54) of corneal tissue
with a substantially circular cross-section transverse to the axis.
7. The system (800, 800', 800") of claim 6, wherein the cylindrical blade (810") is configured
to hold the portion (52, 52', 52", 54) of corneal tissue as the second cutting apparatus
(820, 820', 820") makes the series of cuts to the portion of corneal tissue.
8. The system (800, 800', 800") of claim 7, further comprising a source of hydration
fluid (840), wherein the cylindrical blade (810") is configured to be immersed in
the source of hydration fluid while holding the portion (52, 52', 52", 54) of corneal
tissue, the hydration fluid keeping the portion of corneal tissue hydrated while the
second cutting apparatus (820, 820', 820") cuts the portion of corneal tissue.
9. The system (800, 800', 800") of claim 7, further comprising a cutting stage (850),
wherein the cylindrical blade (810") is configured to be mounted on the cutting stage
as the second cutting apparatus (820, 820', 820") makes the series of cuts to the
portion of corneal tissue.
10. The system (800, 800', 800") of claim 9, wherein the second cutting apparatus (820)
includes a femtosecond laser, wherein a first end of the cylindrical blade (810")
is positioned at the cutting stage (850), and the second cutting apparatus is positioned
to make the series of cuts at a second opposing end of the cylindrical blade.
11. The system (800, 800', 800") of claim 10, further comprising a detection system configured
to determine the position of the portion (52, 52', 52", 54) of corneal tissue for
the second cutting apparatus (820, 820', 820").
12. The system (800, 800',800") of claim 10, wherein the consecutive cuts made by the
femtosecond laser (820) include a first cut made closest to the anterior surface of
the donor cornea (50) and a second cut made closest to the posterior surface of the
donor cornea, the corresponding lenticule (60) including a first surface formed by
the first cut and a second surface formed by the second cut, and the femtosecond laser
is configured to shape at least one of the first surface or the second surface of
the corresponding lenticule to form the corneal implant (10) with a desired refractive
profile.
13. The system (800, 800', 800") of claim 10, wherein the cutting stage (850) includes
an actuator (852) configured to contact the portion (52, 52', 52", 54) of corneal
tissue at the first end of the cylindrical blade (810") and move the portion of corneal
tissue through the cylindrical blade toward the second end as the second cutting apparatus
(820, 820', 820") makes the series of cuts to the portion of the corneal tissue.
14. The system (800, 800', 800") of claim 12, further comprising a robotic arm (870) configured
to retrieve each corresponding lenticule (60) as the second cutting apparatus (820,
820', 820") makes the consecutive cuts and the actuator moves the portion of corneal
tissue through the cylindrical blade.
15. The system of claim 1, wherein the portion (52, 52', 52", 54) of corneal tissue has
a substantially circular cross-section transverse to the axis, and each lenticule
(60) has a substantially circular perimeter.